Radio power supply apparatus



y 2, 1933- J. F. DREYER, JR 1,906,452

RADIO POWER SUPPLY APPARATUS Filed May 28, 1928 i 8 g I Patented May 2, 1933 UNITED STATES PATENT OFFICE JOHN FREDERICK DREYER, JR., OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO ATWATER KENT MANUFACTURING COMPANY, OFPHILADELPHIA, PENNSYLVANIA,

.A. CORPORATION or PENNSYLVANIA RADIO POWER SUPPLY APPARATUS Application filed May 28, 1928. Serial No. 281,078.

My invention relates to radio apparatus and more particularly to radio receiving apparatus in which signal energy is amplified at radio and audio frequencies.

In accordance with my invention, in an arrangement in which grids andanodes of at least one high or radio frequency amplifier tube and one or more low or audio frequency amplifier tubes are supplied from a common source, as for example, of rectified, filtered alternating current and more particularly in which is utilized a resistor common to the input and output circuits of the tubes to bias the grids of the tubes to a desired potential, there is provided resistance and capacity inIa relation preventing reaction between the tube circuits, particularly, modulation of signal energy of radio or carrier frequencies; more specifically, a suitably high resistance is included in a direct current anode circuit of each of one or more audio amplifier tubes in series with the aforesaid common grid-biasing resistor, or equivalent, and acapacity of relatively low magnitude is utilized-to provide apath for currents of audio-frequency around the source of anode current, the aforesaid high resistance, and the grid-biasing resistance, if used.

My invention resides in features 'of arrangementhereinafter described and claimed. i v

' For an understanding of my invention, reference is to be had to the accompanying i drawing in which:

Fig. l is a diagrammatic view ofpart of a radio system and power supply for thermionic tubes utilized therein.

Fig. 2 is a diagrammatic view of a complete radio receiving apparatus and power supply.

Referring to Fig; 1, the input circuit of the tube a tuned, or tunable as by condenser k. receives energy transferred thereto or im-- pressed thereon by radio-frequency transformer t. The amplified signal energy is transferredto subsequent input circuit, as

of a radio-frequency amplifier tube or of a detector tube by the radio-frequency transformer t1. Ultimately or directly the amplified energy is impressed upon the input element t2 of the tube 01 in whose plate circuit there is produced variations of current at audio frequency, which may be impressed or both types of amplifier-may be utilized in a complete apparatus.

The terminals of the input elements or transform-er secondaries remote from the grid are connected to the ne ative terminal of a source HV' of direct current, or rectified filtered alternating current, of suitably high voltage. Between a conductor connected to the filaments or cathodes f of the tubes and the negative terminal of HV is connected a resistor T2. The positive terminal of the source HV is connected to the anodes of the tubes. Thedrop of potential across resistor r2 produced by flow of the anode current of the tubes biases their grids g to a suitable negative value.

T2 is shunted by condenser 03 of small magnitude and of low impedance to currents of high or radio-frequency. vIn the system, as

thus far described, variations of the anode. current at aud1o frequency effect changes in magnitude of the current flowing through resistor a2 and hence of-the biasing poten- For simplicity of ex- To prevent. radio-frequency coupling effects the resistor of the audio-amplifier tube 01, an impedance r1, specifically a resistance, of relatively high value and in the alternating current anode path there is included a condenser 07 of comparatively low value, as .5 microfarads, which by-passes the audio-frequency variations around the resistance r1, the source of anode current HV, and the grid-biasin resistance 72. The current flowing througn resistance 72 remains substantially constant notwithstanding the audio-frequency variations of the anode current of tube 411 and therefore the biasim potential applied to the grid of the radio-irequency amplifier tube 7) is not affected to produce modulation of an incoming carrier wave. To attain comparable results with the commonly utilized arrangement above referred tofu capacity of about 30 microfarads, or more, would necessarily'be utilized.

Referring to Fig. 2, the part thereof within the dotted enclosure represents the sources of alternating current for heating cathodes or filaments of the thermionic tubes of the receiving apparatus and for supplying rectified, filtered alternating current to the anode or anode circuits of the tubes, and to their control electrodes or grid circuits. The alternating current is derived fro a conductors 1 and 2 connected toa source G, asthrough a plug receptacle or lamp socket 3 connecting with the transformer primary t inductively related to secondaries 5, 6, and 7 delivering low voltage alternating current for heating the filaments or cathodes of the vac uum tubes of the receivingset While the secondary 8 delivers current for heating the filament or cathode of the rectifier tube 9 whose'anodes are connected to the terminals of the secondary 10.

Alternating current energy is supplied to the filaments or cathodes f of the tubes V, V1 and V3 by secondary 7, to the heater 7b of the tube V2 by the secondary 6, and to the filament f of the tube V4 by the secondary 5 to render the cathode structures of the several tubes electron'emissive. A terminal of a choke coil L, is connected to condoctor 11 connected to the anodes of tubes V, V1 andVt; to conductor 12through re sistance '1' connected to the anode of the tube" V2, and to conductor 13 through resistance or impedance 71 as in Fig.1 to the anode to earth E and to substantially the mid point of a resistance r3 connected across the terminals of secondary 7.

The grid or input circuit of these tubes is completed through the resistor 12, preferably having small or zero inductance, and the voltage drop across the resistance due in whole or in part to the How of anode current therethrough is as above described utilized to effect a negative biasing potential on the grid of the tubes V, V1 and V3. The

ture, as a loop, etc; In the example illustrated, between the antenna A, earth or counter capacity E is connected the primary of a transformer T, preferably having a step-up ratio of transformation, and across whose secondary is or may be connected the tuningcondenser K whose one terminal is connected through the stabilizing resistance R with the control electrode or grid 9 of the first radio frequency amplifier tube V whose filament or cathode fl is heated as above stated by alternating current from the secondary winding 7 The grid to filament, or input circuit of the tube is completed by condensers 03 connected from the filament terminals to ground. the radio frequency componentof the anode circuit current is through the primary of a radio frequency transformer T1, also preferably of the step-up type, through condensers c2 and 03 to the filament) or cathode The secondary of the transformer T 1 is bridged by tuning condenser K1 a terminal of which is connected through a stabilizing resistance R1 with the grid g of the radio frequency amplifier tube V1, and others whose terminal is connected to ground to complete the input circuit of the tube through condensers 03. In the anode circuit of the tube is connected the primary of radio frequency transformer T2, generally similar to T1, and whose secondary is bridged by the variable condenser K2 between one of whose terminals and the grid 9 of the detector tube V2 is connected the condenser 04 shunted by the usual leak resistance 78. The cathode f of the detector V2 is of the equi-potential type rendered electron-emissive by the heater resistance H through which passes alternating current delivered by the secondary 6, as above described. The cathode f is connected to earth a or counter capacity E and between it and A path of the anode of the tube is connected fixed condenser 05 having low impedance to high or radio frequency currents. In the anode circuit is included the primary of audio fre quency transformer T3 whose secondary is connected in the grid circuit of the audio frequency amplifier tube V3 whose output or anode circuit is coupled by the audio frequency transformer Tel with the input cir-- cuit of the audio frequency amplifier tube V4 whose anode is-connected througha coudenser 66 having low impedance to currents of audio or voice frequency, with one terminal of the magnet within a loud speaker S whose other terminal is connected to a. suitable point upon a resistance r9bridged across the filament of the tube Val. The conductor 11 is connected to the anode of the tube Vl through choke coil L1 having high impedance to alternating or fluctuating currents as of voice or audio frequency.

As the anode current even of the aggregate of several tubes is ordinarily small, the resistor 12 must necessarily be of fairly high magnitude to produce a suitably large direct-current potential drop properly to bias the grids of the tubes. A negative gridbiasing potential is necessary when the filaments are supplied with raw alternating current and should be of such magnitude to insure that tl e grid does notbecome positive with respect to any part of the filament during the signal cycle. lVhile the preferred arrangement is as shown, a resistance may be connected from the positive terminal of the source of current H.V. to the. cathode end of resistor 9 2 to increase the current flowing therethrough. In the system described the resistor W2 is of about 600 ohms resistance. Utilizing this magnitude of resistance the coupling effects between the circuits to which it is common are marked and include feedback, and modulation of the radio frequency currents by the low frequency variations appearing in the anode current of the audio-frequency disturbances, or squawks.

To avoid these effects resistance rl' connected as above described and in the relation explained in F ig. 1 is of relatively high value, for example about 12,000 ohms, to offer considerable impedance to low or audio-frequencies, and between the anodeend terminal of the resistance T1 and the filament-end terminal of the resistance is connected a condenser 07 having, for example, a capacity of .5 microfarads. It will be understood, however, that the values of resistance and capacity used may be variedv withii reasonable limits. The magnitude of capacity, for example, may be decreased to a still lower value in which event the value of resistance required, however, would be larger and would reduce the plate voltage of the tube V3. As the necessary magnitude of resistance increases rapidly as the capacity is decreased, it is impractical, due to plate voltagerequirements, for example, to continue the reduction of capacity. 7

It further will be understood that the resistance r1 may be reactive, i. e. to greater or less extent inductive, or maybe highly lained by ordinarily used arrangements utilizing at least several times that value.

Furthermore, the cathodes of radio frequency and audio frequency tubes of similar or substantially characteristics may be supplied from the same secondary of a transformer whose primary 4: is connected to a source of low frequency power supply G simplifying the power supply for the re-- ceiving apparatus.

It will be understood that tubes V, V1 and V3 maybe of the heater type, as detector tube V2, in which event theiheater elements maybe supplied from a common secondary winding 7 or fromsecondary 6. The equi potential cathodesf of each tube would then be connected to ground with the resistance r2 included in the grid to cathode circuit of each tube. J

Insofar as certain aspects of my invention are concerned, it will be understood that either or both the anode and cathode structures of the tubes may be supplied from a direct current source, as for example, a

power main supplying direct current at a standard commercial. voltage; The anodes of the tubes may be supplied by a shunt feed circuit as is tube Val without departin from my invention although the series feed arrangement shown and descrlbedis preferred.

hat I claim is:

l. A radio receiving system comprising at least one audio frequencyamplifyingtube and one radio frequency amplifying tube, a

common direct-current source of anode current for said tubes, aeonductive impedance common to the grid andanode circuits of audio frequency:amplifying and radio frequency'amplifying tubes, traversed solely by anode current to provide a negative b as.

ing potential'for the grids of said tubes, a

coupling impedance in the anode circuit of one of said tubes, and means for substant ally segregating the paths of the alternating current components of the anode currentsof the different types of tubes comprising a conductive impedance interposed between thepositive terminal of said source and said coupling impedance, and offering substantial impedance to flow of the alternating component of the anode current of said type of tube, and a condenser of substantially lower impedance for said alternating component connected between the cathode of said one of said tubes and a terminal ofsaid coupling impedance remote from the anode of said tube.

2. A radio receiving system comprising at least one audio frequency amplifying tube and one radio frequency amplifying tube, a common direct-current source of anode current for said tubes, a conductive impedance common to the grid and anode circuits of audio frequency amplifying and radio frequency amplifying tubes, traversed solely by anode current to provide a negative biasing potential for the grids of said tubes, a transformer having its primary in the anode circuit of the audio-frequency amplifying tube, and means for substantially segregating the paths of the alternating current components of the anode currents of the different types of tubes comprising a conductive impedance between the positive terminalof said source and said primary, and offering substantial impedance to flow of ZIHCllO-fl'- quency currents, and a condenser of substantially lower impedance to audio-frequency currents connected between the audio-amplifier cathode and a terminal of said primary remote from the audio-amplifier anode.

3. A radio receiving system including a resistor traversed solely by the anode currents of audio-frequency amplifying and radio-frequency amplifying tubes to bias the grids of said tubes, a common source of direct current'anode current, a by-pass condenser in shunt to said resistor, a transformer having its primary in the anode circuit of the audio-frequency amplifying tube and means permitting substant al reduction in the capacity of said condenser without sacrifice of quality of reproduction comprising a resistance traversed only by audioamplifier tube current disposed between the positive terminal of said source and said primary, and a condenser connected between the audio-amplifier cathode and a terminal of said primary remote from the audioamplifier anode, the impedance of said condenser being substantially less for audiofrequencies than the impedance of said resistance, "and the sum of the capacities of said condensers being substantially less than thecapacity of said first condenser if used alone for the same quality of reproduction.

4. A radio receiving system comprising at least one audio frequency amplifying tube and one radio frequency amplifying tube, a common direct current sourceof-anode current for said tubes, a conductive impedance traversed solely by anode current of the rent comprising a substantially high resistance included solely in the anode circuit of the audio amplifier tube between said primary and said source of current, and a condenser of substantially less impedance for audio-frequencies connected directly between the cathode of said audio-amplifier tube and the anode end of said resistance.

JOHN FREDERICK DREYER, JR. 

